Which two options can you use to achieve this goal?

You are responsible for mobile app development for a company. The company develops apps on Windows Mobile, IOS, and Android.
You plan to integrate push notifications into every app.
You need to be able to send users alerts from a backend server.
Which two options can you use to achieve this goal? Each correct answer presents a complete solution.
NOTE: Each correct selection is worth one point.
A. Azure Web App
B. Azure Mobile App Service
C. Azure SQL Database
D. Azure Notification Hubs
E. a virtual machine